1. Field of the Invention
The present invention relates to clamping units used with toolholders in the metal working industry. In particular, the subject invention is directed to a retention device for securing a canister within the body of such a clamping unit.
2. Description of Related Art
FIGS. 1-3 illustrate prior art and, in particular, illustrate a clamping unit 10 for releasably holding a tubular shank 20 of a toolholder 25. The clamping unit 10 has a base member 30 with a longitudinal axis 32 extending therethrough and a forwardly facing exterior surface 34. A bore 36 extends inwardly from the forwardly facing exterior surface 34 for receiving the toolholder shank 20. A lock rod 38 is movable within the base member 30 along the longitudinal axis 32 in a forward and rearward reciprocating motion, wherein the lock rod 38 has at least one longitudinally extending depression 40 and an adjacent ramp 42, such that, in the rearward position (FIG. 1), locking balls 44 are radially displaced by the ramp 42 to engage the toolholder shank 20 within the base member 30 and, in the forward position (FIG. 2), the locking balls 44 retract into the depression 40 and release the shank 20 from the base member 30.
It should be noted that FIGS. 1 and 2 represent an arrangement, wherein the canister sleeve 50 is at least partially secured by a flange 51 secured within the front of the base member 30, while the canister sleeve 50 in FIG. 3 is secured by retention bolts 70. The base member 30 in FIGS. 1 and 2 and the base member 30 in FIG. 3 are different in this respect, but are both adequate to illustrate the prior art.
A canister sleeve 50 (FIG. 3) is mounted within the base member bore 36 and the sleeve outer surface 52 is adjacent to the bore 36 and the sleeve inner surface 54 surrounds at least a portion of the lock rod 38. The canister sleeve 50 has radial apertures 56 for guiding the locking ball 44 between the lock rod 38 and the tubular toolholder shank 20.
A shoulder 58 extends inwardly within the base member bore 36 and the canister sleeve 50 abuts with a stop ring 59, which abuts with the shoulder 58 to limit the rearward motion of the canister sleeve 50. FIG. 3 illustrates a stop ring 59 adjacent to the shoulder 58, however, the canister sleeve 50 may abut directly against the shoulder 58.
In part, the alignment and the stability of the toolholder 25 secured within the clamping unit 10 depends upon the orientation and the rigidity of the canister sleeve 50 within the base member 30. While FIGS. 1 and 2 illustrate a canister sleeve 50 that may be loaded from the rear of the clamping unit 10, FIG. 3 illustrates an arrangement whereby the canister sleeve 50 must be loaded from the front of the clamping unit 10 and it is upon this configuration in which the subject invention is based.
In the past, a retention bore 60 extended through the base member 30 along a retention bore axis 62, wherein the retention bore axis 62 had an axial component, indicated by arrow 64, extending into the base member bore 36. Additionally, the canister sleeve 50 had a slot 66, wherein the slot 66 had a locating surface 68 generally perpendicular to the retention bore axis 62. A retention bolt 70 was threadably mated with the retention bore 60 to contact the canister slot locating surface 68 and clamp the canister sleeve 50 within the base member bore 36.
However, there are clearances between the retention bolt 70 and the retention bore 60 which can lead to flexibility of the canister sleeve 50 mounted within the bore 36. In particular, with respect to FIG. 3, a gap 72 between the retention bolt 70 and the retention bore 60 illustrates such a clearance.
A design is needed to secure the canister sleeve 50 within the bore 36 of the base member 30 with a higher level of rigidity.